In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving frequency usage efficiency and improving the peak data rate, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing frequency usage efficiency and the peak data rate, reducing delay and so on, long-term evolution (LTE) has been under study (non-patent literature 1). Unlike W-CDMA, LTE uses, as multiplexing schemes, OFDMA (Orthogonal Frequency Division Multiple Access) on downlink channels (downlink) and SC-FDMA (Single Carrier Frequency Division Multiple Access) on uplink channels (uplink).
As shown in FIG. 1, a signal to be transmitted on the uplink is mapped to an adequate radio resource and transmitted from a mobile terminal apparatus to a radio base station apparatus. In this case, user data (UE (User Equipment) #1 and UE #2) is allocated to the uplink shared channel (PUSCH: Physical Uplink Shared CHannel). Also, when control information is transmitted at the same time with user data, the control information is time-multiplexed on the PUSCH, and, when control information alone is transmitted, the control information is allocated to the uplink control channel (PUCCH: Physical Uplink Control CHannel). This control information to be transmitted on the uplink includes downlink quality information (CQI: Channel Quality Indicator), retransmission acknowledgement signals (ACK/NACK) for downlink shared channel (PDSCH: Physical Downlink Shared CHannel)) signals, and so on.
The PUCCH typically employs different subframe configurations when transmitting CQIs and when transmitting ACK/NACK (see FIG. 2A and FIG. 2B). The subframe configuration of the PUCCH includes seven SC-FDMA symbols in one slot (½ subframe). Also, one SC-FDMA symbol includes twelve information symbols (subcarriers). To be more specific, in the CQI subframe configuration (CQI format), as shown in FIG. 2A, a reference signal (RS) is multiplexed on the second symbol (#2) and the sixth symbol (#6) in a slot, and control information (CQI) is multiplexed on the other symbols (the first symbol (#1), the third symbol (#3) through the fifth symbol (#5), and the seventh symbol (#7)). Also, in the ACK/NACK subframe configuration (ACK/NACK format), as shown in FIG. 2B, a reference signal is multiplexed on the third symbol (#3) through the fifth symbol (#5) in a slot, and control information (ACK/NACK) is multiplexed on the other symbols (the first symbol (#1), the second symbol (#2), the sixth symbol (#6) and the seventh symbol (#7)). In one subframe, the above slot is repeated twice. Also, as shown in FIG. 1, the PUCCH is multiplexed on the radio resources at both ends of the system band, and frequency hopping (Inter-slot FH) is applied between the two slots having different frequency bands in one subframe.